Arc welding is one of several fusion processes for joining metals. By applying intense heat, metal at a joint between two parts is melted and caused to intermix. Mixing typically occurs with an intermediate molten filler metal. Upon cooling and solidification, a metallurgical bond is formed.
In arc welding, the intense heat necessary to melt metal is produced by an electric arc. The arc is formed between the workpiece and an electrode, typically in the form of a stick or wire that is manually or mechanically guided along the joint. The electrode can be in the form of a rod which serves to carry the electrical current between the rod tip and the workpiece. Or, the electrode may be a specially prepared rod or wire that not only conducts the current but also melts and supplies filler metal to the joint. Most welding in the manufacture of steel products uses the second type of electrode, i.e. a “consumable electrode.”
An arc welding circuit including an AC or DC power source and appropriate controls, is connected by a work or grounding cable to the workpiece and by a “hot” cable to an electrode holder of some type. The electrode holder makes electrical contact with the welding electrode.
When performing arc welding upon a workpiece, the workpiece is typically supported on one or more work stands. This is desirable so that the workpiece is not contacted with water or other fluids on the ground, and to improve accessibility to the workpiece for the operator. Upon placing the workpiece on one or more stands, and prior to performing an electric welding operation, it is necessary to establish a grounding path for the grounding or work cable. Although the grounding cable and its associated clamp can be attached to the workpiece itself, this is not desirable for many applications. For certain welding operations or for certain types of workpieces such as pipes, it is typically necessary to periodically move or rotate the workpiece relative to the work stand(s). This may be necessary to expose new regions of the workpiece and/or joint for welding. If the grounding cable is attached to the workpiece, workpiece movement can disrupt the electrical connection established at the interface of the workpiece and grounding cable. In addition, the grounding cable can interfere with placement of the workpiece on the work stand(s), and in particular, can wind around or otherwise become entangled with the workpiece. As will be appreciated by those skilled in the art, this is undesirable. In fact, many electric welding equipment suppliers provide strict instructions for cabling practices and placement of cables that warn against these scenarios.
In view of these concerns, artisans have proposed various provisions for facilitating attachment of grounding cables to support members which support workpieces to be welded. In addition to the use of readily attachable clamps, various mechanical assemblies have been devised for attaching grounding cables to electrical grounding components (or vise-versa) provided on support members. These assemblies ensure reliable electrical connection at a clamp or support member by an electric arc welder power source. The grounding circuit is completed by physical contact between the workpiece, i.e. pipe, and the clamp or support member.
Although satisfactory in many regards, problems can arise if a relatively large number of mechanical interfaces or electrical discontinuities exist between the workpiece and the grounding cable. If excessive, the electrical resistance between the workpiece and the grounding cable can be impeded and detrimentally affect the welding operation. In addition, gaps between components along the grounding path between workpiece and grounding cable can produce sparks or arcing which, as will be appreciated, are not desirable. Accordingly, it would be desirable to provide provisions and a strategy for further reducing mechanical interfaces and electrical discontinuities along a grounding path and thereby reduce the potential for the occurrence of sparks or arcing.
Another concern associated with electric welding of supported workpieces relates to shifting of the workpiece on one or more support members such as work stand(s). Shifting loads can cause distortion along mechanical interfaces and create or change separation distances along an interface. This in turn, can increase the potential for arcing or sparking, which as previously explained is undesirable. Accordingly, a need exists for a support assembly that is less susceptible to changing and distorting mechanical interfaces along a grounding path upon shifting or changing loads.